1. Field of the Invention
The present invention relates to novel pharmaceutical compositions containing 5-hydroxytryptophane or a derivative of 5-hydroxytryptophane.
2. Description of the Prior Art
The importance of the role of serotonin (5-hydroxytryptamine) as a cerebral intercellular chemical mediator is known (cf. particularly applicant's French Patent Application No. 81-01931). For example, serotonin deficiency conditions cause certain disorders of sleep, depression syndromes and phenylketonuria. The administration of 5-hydroxytryptophane (5-HTP), a direct precursor of serotonin, compensates for this deficiency since serotonin is synthesized from ingested tryptophane according to the following metabolic chain: EQU tryptophane.fwdarw.5-hydroxytryptophane.fwdarw.5-hydroxytryptamine
The administration of 5-HTP is in fact preferable to the administration of a monoamine oxidase inhibitor, which blocks the degradation of both serotonin and other biogenic amines and is therefore sometimes used to increase blood concentrations of serotonin.
Nonetheless, the administration of 5-HTP as an immediate precursor of serotonin presents a considerable drawback: the overall yield of cerebral serotonin actually synthesized with respect to the amount of 5-hydroxytryptophane administered is very low. This conversion level is very low for various reasons; among others, it is due to mediocre passage of the gastrointestinal and hematoencephalic barriers by 5-HTP, considerable decarboxylation of 5-hydroxytryptophane at the peripheral level and high hepatic catabolism of 5-HTP. This loss can be partly compensated for by the simultaneous administration of a peripheral decarboxylase inhibitor, but this addition has other drawbacks.
Accordingly, there remains a need for pharmaceutical compositions containing 5-hydroxytryptophane which overcome these previously known defieciencies.